dt-bindings: phy: cdns,salvo: add property cdns,usb2-disconnect-threshold-microvolt

Add cdns,usb2-disconnect-threshold-microvolt property to address fake USB
disconnection issue during enumeration or suspend state for difference
platform.

Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Frank Li <Frank.Li@nxp.com>
Link: https://lore.kernel.org/r/20230517161646.3418250-7-Frank.Li@nxp.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>

Documentation/devicetree/bindings/phy/cdns,salvo-phy.yaml

@@ -31,6 +31,12 @@ properties:
   "#phy-cells":
     const: 0
 
+  cdns,usb2-disconnect-threshold-microvolt:
+    description: The microvolt threshold value utilized for detecting
+      USB disconnection event.
+    enum: [575, 610, 645]
+    default: 575
+
 required:
   - compatible
   - reg